Revision question · Braking systems

Your vehicle is fitted with a 'diff-lock'. When would you normally use it?

Revision material from the imported DVSA bank includes source-checked Lanekind learning corrections. These corrections are not newly issued official examination questions, and practice does not reproduce a live test paper.

Answer options

While driving on straight roads

While towing an empty trailer

While driving on muddy construction sites

While uncoupling a trailer

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While driving on muddy construction sitesThis was the right answer

The differential allows the drive wheels to rotate at different speeds; this is necessary for the vehicle to negotiate corners and bends. On a slippery surface, however, it can cause problems: if one wheel has less traction, it can spin, resulting in a complete loss of drive. The 'diff-lock' prevents the wheels from turning independently and so helps to stop this happening.

Reviewed reading for this question

Use a differential lock only for suitable low-grip conditionsReviewed guidance summary · Mud and snow can leave a drive wheel without traction; the selected lock helps forward drive but changes steering. The corrected escape question no longer says any movement always requires immediate disengagement.

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